Field of the Invention
Embodiments of the present invention generally relate to methods and apparatus for drilling with casing. More particularly, the present invention relates to methods and apparatus for coupling two strings of casing.
Description of the Related Art
In the oil and gas producing industry, the process of cementing casing into the wellbore of an oil or gas well generally comprises several steps. For example, a conductor pipe is positioned in the hole or wellbore and may be supported by the formation and/or cemented. Next, a section of a hole or wellbore is drilled with a drill bit which is slightly larger than the outside diameter of the casing which will be run into the well.
Thereafter, a string of casing is run into the wellbore to the required depth where the casing lands in and is supported by a well head in the conductor. Next, cement slurry is pumped into the casing to fill the annulus between the casing and the wellbore. The cement serves to secure the casing in position and prevent migration of fluids between formations through which the casing has passed. Once the cement hardens, a smaller drill bit is used to drill through the cement in the shoe joint and further into the formation.
In general, drilling with casing allows the drilling and positioning of a casing string in a wellbore in a single trip. However, installation of multiple casing strings still requires multiple trips. For example, installation of the conductor casing and the installation of surface casing are generally performed using separate trips.
There is a need, therefore, for improved methods and apparatus for coupling two strings of casing. There is also a need for apparatus and methods for drilling and running to casings in a single trip.